In current storage environments or systems, such as block storage systems, it is often the case that such environments or systems will include one or more hosts, such as a server, for example, such as is available from Sun Microsystems and/or other companies. Such hosts are typically attached through network connections, such as a fibre channel, to one or more storage units or arrays. Such storage units or arrays are typically configured as a cabinet including multiple storage disk drives, and onboard intelligence in the form of one or more processors which operate to control the storage unit. Examples of such storage units are those available from EMC Corporation, for example, under the product name Clariion™.
In such environments, multiple input-output (I/O) operations occur due to users working through one or more hosts to read and write data to disks in the storage unit.
The read and write operations correspond to what are generally referred to as individual sessions. For example, a session might involve storing of ticket purchase orders for a concert or other event which occurred beginning at 9:00 a.m. on a Tuesday, and ending at 1:00 p.m. on the same day.
For general backup processing, it is desirable to be able to view all the data for a particular session from a separate host, for example, to support offloading of the backup processing from the host processing the application. However, it becomes difficult to track the data because subsequent sessions by the host which initiated the first session will often change the configuration of the disk, and the way data is stored thereon in a manner such that it becomes impossible to view and access data for a prior session.
One current product currently available from EMC Corporation under the aforementioned Clariion™ name currently supports the ability to view data for a single active session on a disk. Although such a device supports a single session, it is often the case that a host would want to run multiple sessions concurrently. For example, in the aforementioned example concerning ticket sales, the first session may have started at 9:00 a.m., but a user at the host also knows that tickets for a particular and very popular event are due to begin sales at 10:00 a.m. In such a case, it is desirable to run a second session while continuing to run the first session for sales of all tickets from 9:00 a.m. to 1:00 p.m. so as to be able to gather information about which ticket sales were directly attributable to the popular event, and sales for which began at 10:00 a.m. The existing system is incapable of allowing views of multiple sessions. Further, in the event of failure such as the loss of power, etc., the session data will be lost and the session must be manually restarted when the failure has been corrected.
In accordance with the invention, the problem of current systems which support only a single session, and are not able to provide protection against a single point of failure, e.g., SP crash, power failure, etc.